Phase shift enhancement for a microwave ferrite phase shifter



Oct. 21, 1969 uss, 4R 3,474,361

PHASE SHIFT ENHANCEMENT FOR A MICROWAVE FERRITE PHASE SHIFTER Filed July 21, 1967 FIG. I FIG. 3

IO FERRITE 2 I2 H l5 2 4 I? I 2o 4 T I I8 l9 CONDUCTIVE STRIP FIG. 2 FIG. 4

Wma 2 omecnou fiOF MAGNETIC FIELD f INVENTOR MAX L. REUSS, JR.

ATTORNEY United States Patent 3,474,361 PHASE SHIFT ENHANCEMENT FOR A MICRO- WAVE FERRITE PHASE SHIFTER Max L. Reuss, Jr., New Carrollton, Md., assignor to the United States of America as represented by the Secretary of the Navy Filed July 21, 1967, Ser. No. 655,243

Int. Cl. H03h 7/30 US. Cl. 333-31 3 Claims ABSTRACT OF THE DISCLOSURE An improvement in microwave ferrite phase shifters which utilizes conducting strips or shims in combination with the ferrite so that the maximum phase shift available is increased by approximately 20% in comparison with the maximum phase shift available from use of the ferrite alone in the basic phase shifter.

STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION The present invention relates generally to improvements in microwave ferrite phase shifters and the like and more particularly to new and improved ferrite phase shifters wherein conducting strips or shims are located adjacent to the ferrite so that the maximum phase shift available from the phase shifter is increased by approximately 20% without degrading the electrical and thermal properties of the basic phase shifter.

In the field of microwave energy transfer and propagation, it has been the general practice to employ phase shifters utilizing ferrite materials to perform the phase shifting function. Although such devices have served the purpose, it is often desired that a greater maximum phase shift be available from the phase shifter.

SUMMARY OF THE INVENTION The general purpose of this invention is to provide a microwave ferrite phase shifter which embraces all the advantages of similarly employed devices and which also possesses the property of increasing the maximum phase shift available from such similarly employed ferrite devices by approximately 20% without degrading the electrical properties of the basic phase shifter. The invention possesses the additional property of decreasing the peak insertion loss of conventional ferrite phase shifters over a major portion of the frequency band of operation by reducing insertion loss signal spikes. In addition, this invention provides for greater thermal cooling, via greater metal to ferrite contact area, than has heretofor been present in prior art ferrite phase shifters.

An object of the present invention is the provision of phase shift enhancement for microwave ferrite phase shifters which suppresses the negative phase shift mode of microwave energy without affecting the positive phase shift mode so as to result in a greater resultant positive phase shift in the energy.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which like reference numerals designate like parts throughout the figures thereof.

3,474,361 Patented Oct. 21, 1969 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an end view of one embodiment of the invention;

FIG. 2 illustrates a section of the device taken on the line 22 of FIG. 1 looking in a direction of the arrows;

FIG. 3 shows an end view of a second embodiment of the invention; and

FIG. 4 shows a section of the device taken on the line 4-4 of FIG. 3 looking in the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIG. 1 a wave guide 10 which has a ferrite rod 11 centrally located therein and in contact with the two broader sides of the wave guide 10. The ferrite rod 11 is shown with tapered ends in the figures, and the purpose of the tapers is for impedance matching to the wave guides. In addition, conducting strips or shims 12 through 15, which may be tapered, are physically attached to the ferrite rod 11 on opposite sides thereof and at both ends. FIG. 2 shows a section of the wave guide taken on the line 22 of FIG. 1 looking in the direction of the arrows and shows the wave guide end with the tapered ferrite rod 11 centrally located therein; and the conductive strips or shims 13 and 14 are shown physically connected to the ferrite rod 11.

FIG. 3 shows another embodiment of the invention with ferrite rod 11 located within the wave guide 10 in the same manner as disclosed in FIGS. 1 and 2. In addition, conductive strips or shims 17-20 are shown in physical contact with the ferrite rod 11 on both sides and at opposite ends thereof. These shims 17-20 each extend from the ferrite rod 11 to the inner walls of the narrower sides of the wave guide 10. The magnetic field is oriented in parallel relationship with the longitudinal axis of the wave guide 10, as shown in the figures.

It is known that the microwave energy propagated through a wave guide is comprised of a positive phase shift mode and a negative phase shift mode wherein the overall positive phase shift of the energy is the resultant of these two modes. It is also known that the resultant positive phase shift of such microwave energy is dependent upon the position of the ferrite rod which is within the wave guide and upon the dimensions of the ferrite rod. These characteristics are discussed in a report by Dr. I. Snieder, No. Ph. L. 1965-19 of April 1965 which was prepared in the Netherlands for the Physics Laboratory of the National Defense Research Organization TNO. The title of this report is Influence of ,u and K on the Reciprocal Phase Shifter as a Function of Position in the Wave Guide. Thus, where the magnetic field is applied in parallel relation with the longitudinal axis of the wave guide it has been determined that the energy passing through a wave guide, such as wave guide 10 shown in FIG. 1, and through a ferrite rod 11 is subjected to a positive phase shift by that portion of the ferrite rod which is located immediately adjacent to the center of the wave guide 10. It has also been determined that such energy passing through a wave guide is subjected to a negative phase shift by those portions of the ferrite rod 11 which are immediately adjacent to and in physical contact with the broader sides of the wave guide 10.

In the operation of this invention the recognition of the presence of the positive phase shift mode and of the negative phase shift mode within the energy traveling through a wave guide is utilized to increase the maximum phase shift available from the phase shifter. It has been discovered that the negative phase shift created by those portions of the ferrite rod immediately adjacent to and in contact with the broader sides of the wave guide 10, can be suppressed or attenuated by placing conductive strips or shims 12-14, as shown in FIG. 1, in contact with those portions of the ferrite rod 11 which create the negative phase shift in the energy traveling down the wave guide 10. As a result of the suppression of the negative phase shift mode of the microwave energy, the magnitude of the resultant positive phase shift of the microwave energy is greater than it was prior to this suppression of the negative phase shift. Thus, in this way the overall or resultant phase shift which may occur as energy passes through the ferrite rod 11 is increased; and experiments to date have shown that this increase may be as great as 20% when compared with the maximum phase shift available from the basic phase shifter without the addition of the conductive strips or shims.

Similarly, as shown in FIGS. 3 and 4 the strips or shims, which are of a conductive material, can be increased in width so as to contact both the walls of the ferrite rod 11 and the inside walls of the broad and narrow sides of the wave guide 10, thus forming a modified cross wave guide in cross section. This configuration also results in the suppression of the negative phase shift mode of the microwave energy traveling through the wave guide so that the resultant phase shift applied to the energy is greater, by as much as than the maximum phase shift available from the basic phase shifter without the conductive shims 17-20.

This device effectively provides for the phase shift enhancement of microwave ferrite phase shifters in such a way that the maximum phase shift available from the phase shifter is increased by approximately 20% in comparison with the maximum phase shift available from the basic phase shifter without the addition of the conductive strips or shims. This is accomplished without degrading the electrical properties of the basic phase shifter; and the thermal properties of the basic phase shifter are actually improved since the presence of the conductive strips or shims in contact with the ferrite and the walls of the wave guide aids in the thermal cooling of the phase shifter by providing a larger heat sink. In addition, it is an inherent property of this invention that the same maximum phase shift can be attained as was possible by the use of the basic phase shifter by the use of a shorter ferrite rod.

Although it has not been shown in the figures, it should be understood that the conductive strips or shims 12-14 and 17-20 may be tapered in various ways in order to decrease the reflection and loss of energy as the energy travels down the wave guide 10.

Obviously many modifications and variations of the present invention are possible in light of the above teachmgs.

What is claimed and desired to be secured by letters patent of the United States is:

1. A microwave phase shifter, comprising:

a wave guide having a generally rectangular cross section;

an elongated ferrimagnetic member positioned centrally within the wave guide and in physical contact with the two broader walls thereof; and

a plurality of elongated conductive strips abutting only a fraction of the exposed surface area of said ferrimagnetic member, each of said strips being in phys ical contact with at least a broader wall of said wave guide and that portion of said ferrimagnetic member adjacent thereto,

whereby a longitudinally applied magnetic field activates said phase shifter to provide optimum phase shift of microwave signals propagating therethrough.

2. The phase shifter of claim 1 wherein each of said conductive strips are in physical contact with a broader Wall and a narrower wall of said wave guide.

3. The phase shifter of claim 2 wherein said member has tapered ends.

References Cited UNITED STATES PATENTS 3,205,501 9/1965 Kuhn 333--24.l X 3,274,521 9/1966 Nourse 33324.1 2,745,069 5/1956 Hewitt 3331.1 X

OTHER REFERENCES Goodwin: Duplexing a Solid-State Ruby Maser in an X-Band Radar System, Proc. of the IRE, January 1960, p. 113.

HERMAN KARL SAALBACH, Primary Examiner P. L. GENSLER, Assistant Examiner US. Cl. X.R. 333-24.1 

